# How Long is a Jiffy?

Informally, a "jiffy" simply means "a moment" or "quickly." (Think "I'll be there in a jiffy!") But a jiffy can be a precise measurement of time, too, although its definition varies between different fields of study. In astrophysics and quantum physics, a jiffy is the amount of time it takes for light to travel a distance the size of a nucleus. But the absolute smallest definite measurement of time may be the Planck time. The Planck time shares a name with the Planck length, which is the smallest possible length at 1.61619926 × 10^-35 meters. Knowing the Planck length is necessary in determining the smallest possible amount of time. The Planck time is the smallest amount of time, and it can be calculated by dividing the Planck length by the speed of light. The Planck time is something around 10^-43 seconds.

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### Key Facts In This Video

1. The Planck length is the smallest length (it measures 1.61619926 × 10^-35 meters). 00:01

2. The shortest possible time may be the Planck length divided by the speed of light. 00:28

3. The attosecond may be the shortest amount of time that has ever been identified. 01:00